The present invention relates to a novel treating agent for paper and fiber and a process for preparing the same, and more particularly to a treating agent mainly composed of a water-soluble cationic resin available for various fibers such as vegetable fibers, mineral fibers or synthetic fibers, and products therefrom such as papers, non-woven fabrics and fiberboards. Especially, the treating agent of the invention is suitably employing in paper making.
Hitherto, anionic acrylamide polymers have been widely employed as a treating agent in paper making. However, such polymers require a retention aid such as aluminum sulfate and the use thereof is limited to acidic pH range. Therefore, they have defects such as waste water problem, corrosion of paper machine and deterioration of paper.
There have also been proposed various cationic treating agents not requiring a retention aid such as aluminum sulfate.
U.S. Pat. No. 2,926,116 discloses a polyamide-polyamine resin. Such a resin improves dry and wet strengths of paper. However, the foaming tends to occur in sheet forming, and also the drainage and the retention effect for fillers and inferior.
It is known that polyethyleneimine, which is highly cationic, is employed as a wet strength agent, and the application thereof to paper making or the derivative thereof has been reported. Japanese Patent Publication No. 18401/1966 discloses polyethyleneimine-partially hydrolyzed polyacrylamide complex indicating amphoteric polyelectrolyte, which is prepared by adding an aqueous solution of polyethyleneimine to an aqueous solution of partially hydrolyzed polyacrylamide and employed in a form of aqueous solution as a wet and dry strength agent. However, the improvement of wet and dry strengths of paper, the drainage and the retention effect for fillers are not necessarily sufficient. Also, polyethyleneimine-epichlorohydrin strength agent as shown in Japanese Patent Publication No. 14165/1968 improves wet strength, but has disadvantages that the drainage in sheet forming and the retention effect for fillers are poor and the formed sheet is noticeably colored. Further, there has been proposed a treating agent composed of a copolymer of acrylamide and a cationic monomer which is cationic by itself. However, a copolymer of acrylamide and 2-dimethylaminoethyl methacrylate as shown in U.S. Pat. No. 2,838,397 is also poor in the improvement of wet and dry strengths of paper.
Furthermore, there has been known from U.S. Pat. No. 3,507,847 a water-soluble cationic vinyl polymer useful as a wet strength agent in paper making, which is prepared by reacting polyacrylamide with dior poly-amines having at most six amino groups so as to introduce cationic groups to polyacrylamide by deammonification condensation. This cationic polymer can improve wet strength of paper, but the use thereof is limited to a narrow pH range around neutrality and also it is not practical in point of dry strength, retention effect for fillers and drainage. The above U.S. Patent also discloses a strength agent obtained by further subjecting the polyacrylamide-di- or poly-amine reaction product to addition reaction with epichlorohydrin. Epichlorohydrin has the effect of further improving wet strengthening property of the polyacrylamide-di- or polyamine reaction product to some extent and also has the effect of extending the pH range from neutrality to an alkaline range. However, such a strength agent still possesses the above-mentioned disadvantages and is not a satisfactory strength agent.
The present inventors, as a result of studying treating agents for paper or fiber on the basis of the fact that noncationic amide-containing polymers possess an excellent flocculating property and a strengthening property for paper or fiber, and polyalkyleneimines possess an flocculating property and a strengthening property for paper or fiber, particularly an excellent retention ability to fiber, had found that an water-soluble cationic amide-containing resin which was prepared by subjecting an amide-containing polymer to deammonification condensation with polyalkyleneimine, or a water-soluble cationic thermosetting resin obtained by reacting the amide-containing polymer, the polyalkyleneimine and a halohydrin, had excellent effects in treating paper and fiber (see U.S. Patent Application Ser. No. 555,039).